Constitution

A constitution is a set of fundamental principles or established precedents according to which a state or other organization is governed. These rules together make up, i.e. constitute, what the entity is. When these principles are written down into a single collection or set of legal documents, those documents may be said to comprise a written constitution.
Constitutions concern different levels of organizations, from sovereign states to companies and unincorporated associations. A treaty which establishes an international organization is also its constitution, in that it would define how that organization is constituted. Within states, whether sovereign or federated, a constitution defines the principles upon which the state is based, the procedure in which laws are made and by whom. Some constitutions, especially written constitutions, also act as limiters of state power, by establishing lines which a state's rulers cannot cross, such as fundamental rights.
George Washington at Constitutional Convention of 1787, signing of U.S. Constitution.
The Constitution of India is the longest written constitution of any sovereign country in the world, containing 448 articles, 12 schedules and 100 amendments, with 117,369 words in its English language version, while the United States Constitution is the shortest written constitution, at 7 articles and 27 amendments.
Generally, every modern written constitution confers specific powers to an organization or institutional entity, established upon the primary condition that it abides by the said constitution's limitations. According to Scott Gordon, a political organization is constitutional to the extent that it "contain[s] institutionalized mechanisms of power control for the protection of the interests and liberties of the citizenry, including those that may be in the minority."
The Latin term ultra vires describes activities of officials within an organization or polity that fall outside the constitutional or statutory authority of those officials. For example, a students' union may be prohibited as an organization from engaging in activities not concerning students; if the union becomes involved in non-student activities these activities are considered ultra vires of the union's charter, and nobody would be compelled by the charter to follow them. An example from the constitutional law of sovereign states would be a provincial government in a federal state trying to legislate in an area exclusively enumerated to the federal government in the constitution, such as ratifying a treaty. Ultra vires gives a legal justification for the forced cessation of such action, which might be enforced by the people with the support of a decision of the judiciary, in a case of judicial review. A violation of rights by an official would be ultra vires because a (constitutional) right is a restriction on the powers of government, and therefore that official would be exercising powers he doesn't have.
In most but not all modern states the constitution has supremacy over ordinary Statutory law (see Uncodified constitution below); in such states when an official act is unconstitutional, i.e. it is not a power granted to the government by the constitution, that act is null and void, and the nullification is ab initio, that is, from inception, not from the date of the finding. It was never "law", even though, if it had been a statute or statutory provision, it might have been adopted according to the procedures for adopting legislation. Sometimes the problem is not that a statute is unconstitutional, but the application of it is, on a particular occasion, and a court may decide that while there are ways it could be applied that are constitutional, that instance was not allowed or legitimate. In such a case, only the application may be ruled unconstitutional. Historically, the remedy for such violations have been petitions for common law writs, such as quo warranto.